Method and system for real-time fluorescent determination of trace elements

ABSTRACT

A system for real-time fluorescent determination of trace elements comprising means for moving a plurality of samples having at least one trace element along a sample path; means for generating a plurality of incident radiation pulses of different wavelength; means for illuminating at least a respective one of the samples with at least a respective one of the radiation pulses during the movement of the samples, the radiation pulse having a suitable range of fluorescence radiation wavelengths; means for detecting the resultant fluorescence emitted from each of the samples; and first control means in communication with the moving means and the incident radiation generating means for synchronizing the means for illuminating each of the samples with the moving means.

FIELD OF THE PRESENT INVENTION

[0001] The present invention relates generally to spectroscopy systems.More particularly, the invention relates to a method and system forreal-time fluorescent determination of trace elements.

BACKGROUND OF THE INVENTION

[0002] Beginning in the early 1970's, it was found that certainmedicines could be administered in dry-powder form directly to the lungsby inhalation through the mouth or inspiration through the nose. Thisprocess allows the medicine to bypass the digestive system, and in someinstances, allows smaller doses to be used to achieve the same desiredresults as orally ingested medicines.

[0003] Various metered dose powdered inhalers (“MDPI”) or nebulizersthat provide inhalable mists of medicines are known in the art.Illustrative is the devices disclosed in U.S. Pat. Nos. 3,507,277;4,147,166 and 5,577,497.

[0004] Most of the prior art MDPI devices employ powdered medicinecontained in a gelatin capsule. The capsules are typically pierced and ametered dose of the powdered medicine is slowing withdrawn by partialvacuum, forced inspiration of the user or by centrifugal force.

[0005] Several MDPI devices, such as that disclosed in U.S. Pat. No.5,873,360 employs a foil blister strip. Referring to FIG. 1, the foilblister strip 10 includes a plurality of individual, sealed blisters (orpockets) 12 that encase the powdered medicine. The blisters 12 aresimilarly pierced during operation to release the metered dose ofpowdered medicine.

[0006] As will be appreciated by one having ordinary skill in the art,the provision of an accurate dosage of medicine in each capsule orblister is imperative. Indeed, the U.S. Government mandates 100%inspection of MDPI formulations to ensure that the formulations containthe proper amount of prescribed medicine or drug(s).

[0007] Various technologies have been employed to analyze MDPIformulations (i.e., pharmaceutical compositions), such as X-raydiffraction, high-pressure liquid chromatography (HPLC) and UV/visibleanalysis. There are, however, numerous drawbacks associated with theconventional technologies.

[0008] A major drawback of the noted technologies is that most requiresamples to be collected from remote, inaccessible, or hazardousenvironments, and/or require extensive sampling that is time consumingand prohibitively costly. A further drawback is that detection of minuteamounts of trace elements, including the active ingredient or drug(s),is often difficult or not possible.

[0009] It is therefore an object of the present invention to provide amethod and system for high-speed, real-time, on-line fluorescentassessment of active ingredients and trace elements.

[0010] It is another object of the present invention to provide a methodand system for high-speed, real-time, on-line fluorescent detection ofminute amounts of active ingredients and trace elements.

[0011] It is yet another object of the present invention to provide amethod and system for high-speed, real-time, on-line fluorescentdetermination of the identity and concentration of active ingredientsand trace elements.

SUMMARY OF THE INVENTION

[0012] In accordance with the above objects and those that will bementioned and will become apparent below, the system for real-timefluorescent determination in accordance with this invention comprisesmeans for moving a plurality of samples along a sample path; means forgenerating a plurality of incident radiation pulses of differentwavelength; means for illuminating at least a respective one of thesamples with at least a respective one of the radiation pulses duringthe movement of the samples, the radiation pulse having a suitable rangeof fluorescence radiation wavelengths; means for detecting the resultantfluorescence emitted from each of the samples; and first control meansin communication with the moving means and the incident radiationgenerating means for synchronizing the means for illuminating each ofthe samples with the moving means.

[0013] The method for real-time fluorescent determination in accordancewith this invention generally comprises moving a plurality of saidsamples having at least one element along a sample path; generating aplurality of incident radiation pulses of different wavelength;illuminating at least a respective one of the samples with at least arespective one of the radiation pulses during movement of the samples,the radiation pulse having a suitable range of fluorescence radiationwavelengths; detecting the resultant fluorescence emitted from each ofsaid samples; and comparing the detected resultant fluorescencecharacteristics with stored fluorescence characteristics ofpredetermined elements and/or active ingredients to identify the elementor elements in the samples.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Further features and advantages will become apparent from thefollowing and more particular description of the preferred embodimentsof the invention, as illustrated in the accompanying drawings, and inwhich like referenced characters generally refer to the same parts orelements throughout the views, and in which:

[0015]FIG. 1 is a perspective view of a prior art foil blister strip;

[0016]FIG. 2 is a side plan view of the foil blister strip shown in FIG.1;

[0017]FIG. 3 is a flow chart of a conventional blister stripmanufacturing process;

[0018]FIG. 4 is a schematic illustration of the fluorescence detectionmeans according to the invention;

[0019]FIG. 5 is a partial plan view of the radiation transmission means,illustrating the travel of the incident and emitted radiation accordingto the invention;

[0020]FIG. 6 is a further flow chart of a conventional foil blisterstrip manufacturing process, illustrating the incorporation of thefluorescence detection means according to the invention;

[0021]FIG. 7 is a perspective view of a conventional conveyor and thefluorescence detection means according to the invention;

[0022]FIG. 8 is a partial section, front plan view of the conveyor andfluorescence detection means shown in FIG. 7; and

[0023]FIGS. 9 and 10 are graphs of incident radiation versus emissionradiation for prepared compounds, illustrating the detection of lowconcentration active trace elements according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0024] The method and system of the present invention substantiallyreduces or eliminates the drawbacks and shortcomings associated withprior art methods and systems for in-situ detection and analysis oftrace elements. As discussed in detail below, the system generallyincludes fluorescence detection means adapted to provide high-speed,accurate, in-situ determination of the presence, identity andconcentration of trace elements and, in particular, active ingredientsin pharmaceutical compositions. By the term “trace element”, it is meantto mean and include an ingredient, component or element of apharmaceutical composition or MDPI formulation having a relativeconcentration (i.e., % of total) of less than 0.5%, including, but notlimited to, an active ingredient or element and medicament.

[0025] Referring first to FIG. 4, there is shown a schematicillustration of the fluorescence detection means (designated generally20) of the invention. The fluorescence detection means 20 generallycomprises at least one radiation transmission means 22 adapted toprovide incident radiation to the sample 14 and detect the fluorescence(emission) radiation from the sample 14, and first control means 24. Asillustrated in FIG. 3, the first control means 24 preferably includes alight source 26 for providing the desired wavelength of light orradiation to the radiation transmission means 22 via line 23 a, ananalyzer 28 for analyzing the emission radiation detected by theradiation transmission means 22, which is communicated to the analyzer28 via line 23 b, and storage means for storing fluorescencecharacteristics of known elements (or ingredients) for subsequentcomparison with detected emission (fluorescence) radiation from thesample(s) 14.

[0026] As discussed in detail below, the fluorescence detection means 20further includes second control means 29 preferably in communicationwith the light source 26, analyzer 28 and conveyor system 50 forsynchronizing the movement of the samples 14 on the conveyor system 50with the incident radiation transmission and detection of the resultantemission radiation (See FIG. 7).

[0027] As is well known in the art, for fluorescence measurements, it isnecessary to separate the emission (or emitted) radiation from theincident radiation. This is typically achieved by measuring the emissionradiation at right angles to the incident radiation.

[0028] However, as illustrated in FIG. 5, in a preferred embodiment ofthe present invention, the emission radiation, I_(o), is measured (ordetected) along a line I″ that is substantially coincident to the lineI′ defined by the travel of the incident radiation I. According to theinvention, the wavelength of the emission radiation I_(o) is “redshifted” to an upper frequency.

[0029] It is further well established that the relationship between thetrace element concentration and the fluorescence intensity (i.e.,emission radiation) can be derived from Beer's Law, i.e.,

F=ΦP _(o)(1−10^(−∝) bc)  EQ-1

[0030] where:

[0031] F =Fluorescence Intensity

[0032] P₀=Power of incident radiation

[0033] ∝=Molar Absorbtivity

[0034] b=Path length

[0035] c=Sample concentration (moles/liter)

[0036] Φ=Quantum yield−a proportionality constant and a measure of thefraction of absorbed photons that are converted into fluorescentphotons.

[0037] It is thus evident that the quantum yield, Φ, is generally lessthan or equal to unity. It is further evident from Eq. 1 that if theproduct ∝bc is large, the term 10^(∝bc) becomes negligible compared to1, and F becomes constant:

F=ΦP ₀  Eq. 2

[0038] Conversely, if the product ∝bc is small (≦0.01), it can be shown(i.e., Taylor expansion series) that the following provides a goodapproximation of the fluorescence intensity:

F=2.303ΦP ₀ ∝bc  Eq. 3

[0039] Accordingly, for low concentrations of trace elements, thefluorescence intensity is directly proportional to the concentration.The fluorescence intensity is also directly proportional to the incidentradiation.

[0040] Since the noted relationships hold for concentrations up to a fewparts for million, Eq. 3 is preferably employed in the method of theinvention to determine the concentration of the trace element(s)detected by the fluorescence detection means 22.

[0041] Referring now to FIG. 3, there is shown a flow chart of aconventional blister strip process, illustrating the primary stepsinvolved in the manufacture of a foil blister strip. According to theprocess, the base foil is fed from a coil 30 to the forming operation32.

[0042] After the blisters 12 are formed on the strip 10 (see FIGS. 1 and2), the strip 10 is inspected for defects 34 and, in particular, pinholes. Each blister 12 on the strip 10 is then filled 38 with a desiredMDPI formulation or pharmaceutical composition.

[0043] After filling, the strip 10 is subjected to a second inspection40. The second inspection typically comprises a complete chemicalanalysis of the pharmaceutical composition to determine the presence ofall ingredients or elements and the respective concentrations thereof

[0044] As discussed above, the noted inspection 40 typically involvesthe removal of a sample, transfer of the sample to an off-line locationor facility, and HPLC or UV/vis analysis. The operation is thus timeconsuming and expensive.

[0045] After the inspection 40, the appropriate code is applied 42 tothe strip 12. The strip is then transferred to a storage roll.

[0046] Referring now to FIG. 6, there is shown a further flow chart ofthe above discussed blister strip process, illustrating theincorporation of the fluorescence detection means 20 of the invention.As illustrated in FIG. 6, the fluorescence detection means 20 ispreferably disposed between the filling 38 and sealing 40 operations.

[0047] As will be appreciated by one having ordinary skill in the art,the fluorescence detection means 20 of the invention is readilyadaptable to most processes. Further, due to the inherent accuracy andtight specifications (that are possible by virtue of the detection means20), the conventional inspection (i.e., analysis) operation/step 38 canbe eliminated. However, as illustrated in FIG. 6, the fluorescencedetection means 20 can also be employed in conjunction with theconventional inspection operation 38 (shown in phantom).

[0048] Referring to FIGS. 7 and 8, the fluorescence detection means 20of the invention will now be described in detail. Referring first toFIG. 7, there is shown a conventional conveyor system 50 adapted tofacilitate the transfer of two blister strips 10 a, 10 b to the abovenoted operations 30, 32, 36, 20, 40, 42. As illustrated in FIG. 7, theradiation transmission means 22 is disposed proximate the conveyorsystem 50 and, hence, blister strips 10 a, 10 b positioned thereon.

[0049] In a preferred embodiment of the invention, the radiationtransmission means 22 comprises a J. Y. Horiba fluorometer that isadapted to provide two lines of incident radiation (or incidentradiation pulses) 25 a, 25 b. According to the invention, the first lineof incident radiation 25 a is directed toward and substantiallyperpendicular to the first blister strip 10 a and, hence, sample path(designated generally SP₁) and the second line of incident radiation 25b is directed toward and substantially perpendicular to the secondsample path (designated generally SP₂ ). In additional envisionedembodiments of the invention, not shown, the radiation transmissionmeans 22 is adapted to provide one line of incident radiation (e.g., 25a) to facilitate a single (rather than dual) blister strip process.

[0050] In a preferred embodiment of the invention, the first controlmeans 24 generates and provides a plurality of incident radiation pulsesof different wavelengths, preferably in the range of 200 to 800 nm.According to the invention, at least a respective one of the samples 14is illuminated with at least a respective one of the incident radiationpulses as it traverses a respective sample path SP₁, SP₂ . In apreferred embodiment, each sample 14 passing under the radiationtransmission means 22 is illuminated with incident radiation over apre-determined, suitable range of wavelengths capable of inducing afluorescence response in at least one target element (or ingredient).

[0051] Applicants have found that the noted incident radiationwavelength range will induce a definitive fluorescence response in traceelements and, in particular, active ingredients, having a relativeconcentration in the range of 0.3 to 0.5%.

[0052] As discussed above, the emission (fluorescence) radiation isdetected by the radiation transmission means 22 and at least a firstsignal indicative of the sample fluorescence characteristics iscommunicated to the analyzer 28. According to the invention, theemission radiation is then compared to the stored fluorescencecharacteristics of known elements to identify the element or elements(or trace element(s)) in the samples 14. The concentration of theelement(s) can also be determined through the formulations referencedabove (e.g., Eq. 3).

[0053] As also indicated above, the fluorescence detection means 20 isfurther adapted to be in synchrony with the conveyor system 50. In apreferred embodiment of the invention, the fluorescence detection means20 includes second control means 29 that is in communication with thefirst control means 24 and conveyor system 50. The second control means29 is designed and adapted to synchronize the movement of the samples 14on the conveyor system 50 with the illumination of each sample 14 as ittraverses a respective sample path SP₁, SP₂ . Thus, 100% inspection ofeach sample 14 contained in the blisters 12 is ensured.

[0054] Further, the noted synchronized sample fluorescence detection andanalysis is preferably accomplished at a rate (or speed) ofapproximately 1 sample/sec. Thus, the method and system of the inventionprovides high speed, accurate, on-line analysis of MDPI formulations andother pharmaceutical compositions that is unparalleled in the art.

[0055] The present invention will now be illustrated with reference tothe following examples. The examples are provided for illustrativepurposes only, and are not intended to limit the scope of the invention.

EXAMPLE 1

[0056] A MDPI formulation comprising >99.5% lactose and <0.5% activeingredient was prepared. Referring to FIG. 9, the MDPI formulation and areference lactose sample were then subjected to a pre-determined,suitable range of incident radiation to induce a fluorescent response.As will be appreciated by one having ordinary skill in the art, theincident radiation is determined by and, hence, dependent upon thetarget ingredient or element of the MDPI formulation.

[0057] As illustrated in FIG. 9, a definitive fluorescent response,reflecting the detection of the active ingredient was provided with anincident radiation level in the range of approx. 350 mn to 500 nm. Thenoted fluorescence spectra further indicates that an active ingredientor trace element having a relative concentration of less than 0.5% canreadily be detected by virtue of the fluorescence detection means of theinvention.

[0058] As will be appreciated by one having ordinary skill in the art,the noted fluorescence spectra can be compared to stored calibration (orreference) spectra by conventional means to identify the detected activeingredient (or trace element). Further, as discussed above, theconcentration of the detected active ingredient can also be determinedthrough known formulations (See Eq. 3).

[0059] Applicants have further found that subjecting the MDPIformulation to subsequent incident radiation in the same range provideslittle, if any, variation in the detected emission radiation. Indeed,the fluorescence spectra obtained were virtually identical.

[0060] Accordingly, by virtue of the fluorescence detection means of theinvention, a tolerance level of ±0.5 nm (i.e., calibration emissionradiation ±0.5 mn) can be employed. As will be appreciated by one havingordinary skill in the art, the noted tight “QC” specification isunparalleled in the art.

EXAMPLE 2

[0061] Referring now to FIG. 10, there are shown the fluorescencespectra of similar MDPI formulations having ˜0.43% active ingredient(Curve A); ˜0.42% active ingredient (Curve B); ˜0.41% active ingredient(Curve C); ˜0.39% active ingredient (Curve D); and ˜0.37% activeingredient (Curve E). The noted fluorescence spectra were similarlyinduced with an incident radiation level in the range of approximately350 to 500 nm.

[0062] The fluorescence spectra (i.e., Curves A-E) further demonstratethat a sharp, definitive fluorescent response can be achieved in activeingredients having a relative concentration in the range of approx.0.37% to 0.43% by virtue of the fluorescence detection means of theinvention.

[0063] As will be appreciated by one having ordinary skill in the art, anarrower band or range of incident radiation (e.g., 375-475 mn) couldalso be employed to identify and determine the relative concentration ofan active ingredient. Further, an even narrower range of incidentradiation wavelengths (e.g., 400-425 nm) or incident radiation with asingle wavelength within the noted range (e.g., 410 nm) could beemployed to determine active ingredient “presence”.

SUMMARY

[0064] From the foregoing description, one of ordinary skill in the artcan easily ascertain that the present invention provides a method andsystem for high speed, real-time, 100% fluorescent inspection of MDPIformulations and other pharmaceutical compositions. The method andsystem of the present invention further provides an accuratedetermination of (i) the presence (i.e., qualitative assessment), and(ii) identity and concentration (i.e., quantitative assessment) ofactive ingredients and/or other trace elements having a relativeconcentration in the range of approximately 0.3 to 0.5%

[0065] Without departing from the spirit and scope of this invention,one of ordinary skill can make various changes and modifications to theinvention to adapt it to various usage and conditions. As such, thesechanges and modifications are properly, equitably, and intended to be,within the full range of equivalence of the following claims.

What is claimed:
 1. A system for use in in-situ analysis ofpharmaceutical samples, said system comprising: means for holding aplurality of said samples; means for moving said plurality of samplesalong a sample path; means for generating a plurality of incidentradiation pulses of different wavelength; means for illuminating atleast a respective one of said samples with at least a respective one ofsaid radiation pulses during said movement of said samples, saidradiation pulse having a suitable range of fluorescence radiationwavelengths; means for detecting the resultant fluorescence emitted fromeach of said samples; first control means in communication with saidmoving means and said incident radiation generating means forsynchronizing said means for illuminating each of said samples with saidmoving means.
 2. The system of claim 1, including second control meansfor analyzing second resultant fluorescence emitted from each of saidsamples.
 3. The system of claim 1, wherein said range of fluorescenceradiation wavelengths is in the range of 200 to 800 mn.
 4. A system foruse in determining the presence and concentration of trace elements in asample, said system comprising: means for holding a plurality of saidsamples, each of said plurality of samples including at least one ofsaid trace elements; means for moving said plurality of samples along asample path; means for generating a plurality of incident radiationpulses of different wavelengths; means for illuminating at least arespective one of said samples with at least a respective one of saidradiation pulses during said movement of said samples, said radiationpulse having a suitable range of fluorescence radiation wavelengths;means for detecting the resultant fluorescence emitted from said traceelement; and first control means in communication with said moving meansand said incident radiation generating means for synchronizing saidmeans for illuminating each of said samples with said moving means. 5.The system of claim 4, including second control means for storingfluorescence characteristics of pre-determined elements and means forcomparing said detected resultant fluorescence emitted from said traceelement to identify said trace element in said plurality of samples,said second control means including means for determining the relativeconcentration of said trace element in each of said samples.
 6. Thesystem of claim 4, wherein said trace element has a relativeconcentration in the range 0.3 to 0.5%.
 7. The system of claim 4,wherein said range of fluorescence radiation wavelength is in the rangeof 200 to 800 nm.
 8. A system for use in in-situ analysis ofpharmaceutical composition samples, said system comprising; means forholding a plurality of samples, said samples including at least onetrace element; means for substantially simultaneously moving saidplurality of samples along a sample path, illuminating at least arespective one of said samples with incident radiation having one ormore suitable wavelengths during said movement of said plurality ofsamples, and detecting the result in emission radiation from saidsamples; and control means in communication with said illuminating anddetecting means for providing said range of fluorescence radiation andanalyzing said result and fluorescence emitted from said samples.
 9. Thesystem of claim 8, wherein said incident radiation is directed along afirst radiation path that intersects said sample path and issubstantially perpendicular thereto.
 10. The system of claim 9, whereinsaid emitted radiation is substantially detected along a secondradiation path, said second radiation path being substantiallycoincident with said first radiation path.
 11. The system of claim 8,wherein said samples are moved by said moving means at a minimum rate ofone sample per second.
 12. The system of claim 8, wherein said incidentradiation has a plurality of different wavelengths in the range of 200to 800 nm.
 13. The system of claim 8, wherein said trace element has arelative concentration in the range of 0.3 to 0.5%.
 14. A method forin-situ analysis of solid samples, said method comprising the steps of:moving a plurality of said samples along a sample path; generating aplurality of incident radiation pulses of different wavelength;illuminating at least a respective one of said samples with at least arespective one of said radiation pulses during said movement of saidsamples, said radiation pulse having a suitable range of fluorescenceradiation wavelengths; detecting the resultant fluorescence emitted fromeach of said samples; and comparing said detected resultant fluorescencecharacteristics of pre-determined elements to identify the elements insaid samples.
 15. The system of claim 14, wherein said samples are movedby said moving means at a minimum rate of one sample per second.
 16. Thesystem of claim 14, wherein said incident radiation has a plurality ofdifferent wavelengths in the range of 200 to 800 nm.
 17. A method forin-situ analysis of solid samples, said method comprising the steps of:substantially simultaneously moving a plurality of said samples along asample path, illuminating at least a respective one of said samples withincident radiation having one or more suitable wavelengths during saidmovement of said plurality of samples, and detecting the result inemission radiation from said samples; and comparing said detectedresultant fluorescence characteristics of pre-determined elements toidentify the elements in said samples.
 18. The system of claim 17,wherein said samples are moved by said moving means at a minimum rate ofone sample per second.
 19. The system of claim 17, wherein said incidentradiation has a plurality of different wavelengths in the range of 200to 800 nm.